The present invention relates to systems and methods for controlling exhaust smoke produced by an internal combustion engine.
In an effort to reduce exhaust gas emissions, many internal combustion engines incorporate an exhaust gas recirculation (EGR) circuit. The exhaust gas recirculation circuit typically includes an EGR valve which diverts engine exhaust gases from the engine exhaust manifold to the engine intake manifold. This portion of the engine exhaust gas is mixed with clean air and fuel before entering the engine""s combustion cylinders to lower combustion temperature and reduce certain exhaust gas emissions.
For engines using EGR during transient conditions, boost levels may drop below a desired value for EGR control. This results in poor air/fuel ratio and periods of visible black exhaust smoke. Prior art systems and methods have implemented feed forward control to limit this effect. While feed forward control has reduced the visible black exhaust smoke, the problem has not been eliminated.
Therefore, a need exists for a system and method for managing the EGR circuit under transient conditions to significantly reduce or eliminate visible black exhaust smoke.
In accordance with an aspect of the present invention, a method for controlling an internal combustion engine having an EGR circuit is provided. The EGR circuit has an exhaust gas recirculation valve for diverting exhaust gas from an engine exhaust to an engine intake. The method includes ascertaining a predefined threshold based on at least one engine operating condition and preventing the EGR valve from opening if the at least one engine operating condition is below the predefined threshold.
In accordance with another aspect of the present invention the at least one operating condition is current EGR boost pressure.
In accordance with another aspect of the present invention the predefined threshold is a function of engine speed and engine load.
In accordance with another aspect of the present invention the method further comprises accessing a look-up table having a predefined threshold stored therein.
In accordance with another aspect of the present invention, the method includes determining whether EGR gas is flowing.
In accordance with another aspect of the present invention, the method includes sensing a current engine speed.
In accordance with another aspect of the present invention, the method includes determining a current engine load.
In accordance with yet another aspect of the present invention, a computer readable storage medium is provided having instructions stored thereon that are executable by a controller to perform a method of controlling an internal combustion engine, the engine including a variable geometry turbocharger (VGT) and an exhaust gas recirculation (EGR) system. The EGR system includes an EGR valve. The medium has instructions for ascertaining a predefined threshold based on at least one engine operating condition and instructions for preventing the EGR valve from opening if the at least one engine operating condition is below the predefined threshold.
The above features, benefits and advantages and other features, benefits and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken together with the accompanying drawings.